Ding ding ding.
I think, aside from the issues with downvoting, upvoting by nature slowly creates hivemind, circle jerk communities that quickly start to lack any real critical thinking.
Go check out just about any subreddit and it becomes very apparent what illogical silly ideas dominate. If you are logical but uncontroversial you'll get ignored which is just as bad as the controversial opinions which get downvoted to hell. You start to wonder if the confirmation bias we are all building towards is more dangerous than just being uninformed.
There's lots of research on voting behavior in political science, I'm slightly surprised more hasn't been down with it.